1. Field of the Invention
The present invention is directed generally to an information retrieval system, and more particularly, to an information retrieval system to which neural network techniques and genetic algorithms are applied.
2. Description of the Prior Arts
A variety of information retrieval techniques have hitherto been utilized. Recently, however, in a set of image-oriented data such as an image databases and voice databases, there has been an increasing necessity for executing a retrieval under ambiguous conditions with partial characteristics of the accumulated data serving as a key. A system for executing this kind of retrieval has been conventionally actualized in a so-called von Neumann computer in terms of software. FIG. 8 is a block diagram illustrating, e.g., a conventional information retrieval system. The information retrieval system depicted in this Figure is intended to retrieve an original image with the (partial) characteristics of the image inputted by the retriever from the image database in which the images are classified according to the characteristics. Designated at 1 in the same Figure is a memory for storing a database obtained by classifying images according to a variety of characteristics. The numeral 2 represents a characteristic extractor for extracting characteristics from image inputs inputted for retrieving data from the database thereof; and 3 a data retriever for obtaining a desired image data output by searching the memory 1 on the basis of the characteristics extracted by the characteristic extractor 2.
Next, the operation of the prior art information retrieval system will be explained. Assumed is a case where the retriever does not have sufficient information on the object to be retrieved--this could be a case where the retriever carries out the retrieval to specify a person who cannot be clearly remembered and on whom the only information consists of facial characteristics from photographs stored in the memory after a single prior meeting.
FIG. 9 is a flowchart illustrating procedures. When the retrieval information (e.g., portraits) for a judgment is inputted by the retriever, the characteristics thereof are extracted by the characteristic extractor 2 and sent to a data retrieval system 3. The data retrieval system 3 reads one unit-i.e., a sheet of facial photo-of information stored as database in the memory (step ST1).
Next, the data retrieval system 3 performs a scanline decomposition or pixel decomposition of the read facial photo. Based on this, the characteristic portions corresponding to the above-mentioned retrieval information are extracted (step ST2). These portions are collated with the characteristics extracted from the retrieval information by the characteristic retriever 2 (step ST3). As a result, if an evaluation of collation is acceptable, the facial photo is displayed on an unillustrated display (step ST4), and the operation is then finished. Whereas if not acceptable, the operation is returned to step ST1. The next facial photo is read, the same operation is repeated till a desired facial photo is detected.
The conventional information retrieval system is constructed as outlined above and has critical defects as follows. Assuming that there is an image database accumulating facial photographs as data to be retrieved in the memory 1, the facial photo data is expressed by, e.g., N-pieces of pixels each having a degree of freedom of 1 bit. Further assuming that an input information as a key for retrieving image data from the database cannot be described sufficiently, namely, can only be described somewhat ambiguously, expressing partial facial characteristics, the number of partial characteristics of a face will be in the order of an exponential function of the pixel number "N". Accordingly, storing all such characteristics with addresses in the memory 1 with the characteristics serving as a key and with all the stored characteristics being sequentially compared with each other, an "explosion of number of cases" is inevitable. Further, if the partial facial characteristics containing an ambiguity must be specified, e.g., "a square-faced outline" by a program based on von Neumann type processing, there exists a problem that "an extreme intricacy of program" is required.
It is an object of the present invention, which has been devised to obviate the problems described above, to provide an information retrieval system capable of obtaining a result of retrieval on the basis of key retrieval information containing an ambiguity within a range of realistic processing time, wherein a program has a substantially realistic degree of intricacy.